Most recently, the 3.8 million tonne per year plant had been scheduled to start in April and Ivanhoe said the early hot commissioning is four months ahead of the original development schedule. It doubles the size of the mine's concentrator plant. 

Ivanhoe's co-chair Robert Friedland said the commissioning is a big step towards establishing Kamoa-Kakula as one of the two largest copper mining complexes on Earth - with a mine life that "will last for generations". 

"Kamoa-Kakula is by far the greenest and highest-grade major copper producer in the world," Friedland said. 

"As phase two is handed over to our operations team, the projects team will now turn its focus to the phase-three expansion, which is scheduled to begin operations by the end of 2024," he added. 

The start-up of phase two comes less than 10 months after the phase-one plant began operations and both were ahead of schedule and under budget, he said. 

The company noted that over the past six months, the phase-one plant had consistently exceeded design ore throughput by about 10%-15%. 

"Given the experience gained by our operations team during the ramp up of the phase-one plant, we anticipate the ramp up of the phase-two plant will go even smoother," Friedland said. 

Over the past 52-weeks, Ivanhoe's share price on the Toronto Stock Exchange has seen a high of C$13.15 (US$10.45) and low of C$6.27. On March 22, it closed the session at C$11.51. 

Ivanhoe had a market capitalisation of C$13.93 billion.